Character classification

Each of these routines tests a specified single-byte character, wide character, or multibyte character for satisfaction of a condition. (By definition, the ASCII character set between 0 and 127 are a subset of all multibyte-character sets. For example, Japanese katakana includes both ASCII and non-ASCII characters.)

The test conditions are affected by the setting of the LC_CTYPE category setting of the locale. For more information, see setlocale. The versions of these functions without the _l suffix use the current locale for this locale-dependent behavior; the versions with the _l suffix are identical except that they use the locale parameter passed in instead.

Generally these routines execute faster than tests you might write and should be favored over. For example, the following code executes slower than a call to isalpha(c):

if ((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z'))
    return TRUE;

Character-classification routines

Routine	Character test condition
isalnum, iswalnum, _isalnum_l, _iswalnum_l, _ismbcalnum, _ismbcalnum_l, _ismbcalpha, _ismbcalpha_l, _ismbcdigit, _ismbcdigit_l	Alphanumeric
_ismbcalnum, _ismbcalnum_l, _ismbcalpha, _ismbcalpha_l, _ismbcdigit, _ismbcdigit_l	Multibyte alphanumeric
isalpha, iswalpha, _isalpha_l, _iswalpha_l, _ismbcalnum, _ismbcalnum_l, _ismbcalpha, _ismbcalpha_l, _ismbcdigit, _ismbcdigit_l	Alphabetic
isascii, __isascii, iswascii	ASCII
isblank, iswblank, _isblank_l, _iswblank_l, _ismbcsblank, _ismbcsblank_l	Blank (space or horizontal tab)
iscntrl, iswcntrl, _iscntrl_l, _iswcntrl_l	Control
iscsym, iscsymf, __iscsym, __iswcsym, __iscsymf, __iswcsymf, _iscsym_l, _iswcsym_l, _iscsymf_l, _iswcsymf_l	Letter, underscore, or digit
iscsym, iscsymf, __iscsym, __iswcsym, __iscsymf, __iswcsymf, _iscsym_l, _iswcsym_l, _iscsymf_l, _iswcsymf_l	Letter or underscore
isdigit, iswdigit, _isdigit_l, _iswdigit_l, _ismbcalnum, _ismbcalnum_l, _ismbcalpha, _ismbcalpha_l, _ismbcdigit, _ismbcdigit_l	Decimal digit
isgraph, iswgraph, _isgraph_l, _iswgraph_l, _ismbcgraph, _ismbcgraph_l, _ismbcprint, _ismbcprint_l, _ismbcpunct, _ismbcpunct_l, _ismbcblank, _ismbcblank_l, _ismbcspace, _ismbcspace_l	Printable other than space
islower, iswlower, _islower_l, _iswlower_l, _ismbclower, _ismbclower_l, _ismbcupper, _ismbcupper_l	Lowercase
_ismbchira, _ismbchira_l, _ismbckata, _ismbckata_l	Hiragana
_ismbchira, _ismbchira_l, _ismbckata, _ismbckata_l	Katakana
_ismbclegal, _ismbclegal_l, _ismbcsymbol, _ismbcsymbol_l	Legal multibyte character
_ismbcl0, _ismbcl0_l, _ismbcl1, _ismbcl1_l, _ismbcl2, _ismbcl2_l	Japan-level 0 multibyte character
_ismbcl0, _ismbcl0_l, _ismbcl1, _ismbcl1_l, _ismbcl2, _ismbcl2_l	Japan-level 1 multibyte character
_ismbcl0, _ismbcl0_l, _ismbcl1, _ismbcl1_l, _ismbcl2, _ismbcl2_l	Japan-level 2 multibyte character
_ismbclegal, _ismbclegal_l, _ismbcsymbol, _ismbcsymbol_l	Non-alphanumeric multibyte character
isprint, iswprint, _isprint_l, _iswprint_l, _ismbcgraph, _ismbcgraph_l, _ismbcprint, _ismbcprint_l, _ismbcpunct, _ismbcpunct_l, _ismbcblank, _ismbcblank_l, _ismbcspace, _ismbcspace_l	Printable
ispunct, iswpunct, _ispunct_l, _iswpunct_l, _ismbcgraph, _ismbcgraph_l, _ismbcprint, _ismbcprint_l, _ismbcpunct, _ismbcpunct_l, _ismbcblank, _ismbcblank_l, _ismbcspace, _ismbcspace_l	Punctuation
isspace, iswspace, _isspace_l, _iswspace_l, _ismbcgraph, _ismbcgraph_l, _ismbcprint, _ismbcprint_l, _ismbcpunct, _ismbcpunct_l, _ismbcblank, _ismbcblank_l, _ismbcspace, _ismbcspace_l	White-space
isupper, iswupper, _ismbclower, _ismbclower_l, _ismbcupper, _ismbcupper_l	Uppercase
_isctype, iswctype, _isctype_l, _iswctype_l	Property specified by desc argument
isxdigit, iswxdigit, _isxdigit_l, _iswxdigit_l	Hexadecimal digit
_mbclen, mblen, _mblen_l	Return length of valid multibyte character; result depends on LC_CTYPE category setting of current locale

See also

Universal C runtime routines by category